[w3c/manifest] Microsoft's company url redirects to another Microsoft url (#837)

Ran the spec through the [w3 validator](https://validator.w3.org/checklink?uri=https%3A%2F%2Fwww.w3.org%2FTR%2Fappmanifest%2F&hide_type=all&recursive=on&depth=&check=Check) and noticed the issue below

> warning Line: 1052 https://microsoft.com/ redirected to https://www.microsoft.com/en-us/
Status: 301 -> 200 OK
This is a permanent redirect. The link should be updated.

Sending a PR to fix this.

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https://github.com/w3c/manifest/issues/837